i'm currently developing an app for both Android and iOS, thing is... I started with Android and my app has several Activities with different layouts (Screens with different GUI's, if you are not familiar with android), most of them display very different contents; maps, lists with data from databases, images, text fields with buttons and so on (And most of the time the orientation of the screen changes).
The problem comes with iOS:
How do I create more windows from IBActions? (Is this a correct approach?).
Once I create a Window, how do I create a new Interface? (Do I need another .xib file?)
If once the user finishes with one Windows, does the previous window remains in memory and can be re-opened? (Can I use a navigation tab, even though the first windows was not a using it?) This is a major problem since iPhones do not have a back button and Android relies a lot on those...
Also, if I can't split my program in several windows, wouldn't my app use a lot of memory from destroying and building views?
I'm new to Cocoa development and I have already read a book about Objective C programming (which only teaches syntax and so on), another one about simple iPhone apps (all of them were done in one window, changing the views programmatically) and I'm currently reading another one, but i'm unable to find a simple answer to my problem...
I mean I get Obj-C and how to build iPhone apps (well kind-of) but maybe the problem is that I come from a more straight forward development in Android. Each time I see an iOS project, I see it like a total mess, and the documentation in developer.apple.com doesn't help much either, I'm unable to find what I want.
Hope someone has gone through this already and is willing to point me in the right direction, thank you!
I recommend that you start with the View Controller Programming Guide at the apple developer web site. I think you will find it very helpful.
To answer your questions, you can develop each of your views independently. You depending on your purposes, developing each from a nib file could work. In the app I'm working on now, I have some that I develop programmatically and some that I bring in from NIB files. It's all up to you. The guide I mention above discusses both approaches.
Regarding loading views from button presses, you can do that. Depending on the view controller you use, it can be very easily accomplished. WIth the navigation controller, for example, you just create an instance of the view and push it onto the stack. When you're done with the view, you pop it off and your back to your previous view.
With regards to memory, that is always a concern. You might want to take a look at The Memory Management Programming Guide.
Good luck. I'm just starting out with Android development myself.
Chris already provided a great answer but there are a couple of points I want to add to adress specific questions.
iOS apps normally only have a single UIWindow. Within that window you may present multiple views.
Apps are normally organized into several logical screens worth of content, each managed by some UIViewController subclass.
Each UIViewController instance has a root view which may contain many subviews. A UIViewController's view is expected to fill its window or some frame provided by one of Apple's container view controller classes (UINavigationController, UITabBarController, UISplitViewController, and so on). You should not add one UIViewController's view as a subview of another UIViewController's view.
UIViewControllers will attempt to unload their views when the application receives a memory warning if the view is not visible. See the class' life cycle methods like -viewDidUnload. You should support and take advantage of this behavior to reduce your memory footprint. Keeping UIViewControllers in memory without their views loaded should have a minimal overhead, allows you to keep some persistent state, and each controller's view can be reloaded when needed.
Normally to transition between views a control will send a message to the current view controller (often via an IBAction binding). The current controller will then trigger a transition to another view controller. It might do so by creating a new view controller and pushing it onto the current navigation controller or presenting the new controller as a modal. It might have a reference to some existing controller and present that. It might dismiss itself from a navigation stack to reveal the previous controller. It might even pass the message up the controller's hierarchy until some parent switches the visible tab, dismisses or presents a modal, and so on.
You might also trigger smaller transitions by responding to an IBAction by adding, removing, hiding, or moving subviews of a UIViewController's root view.
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Related
What are the advantages of using segues vs managing view controllers and subviews like we did pre-iOS 5.
Pre iOS 5 I might:
Build XIB files for my various Views then do something like [myVC.view addSubView:newVC.view];
vs Segues
You get the advantage of working with storyboards and the functionality of passing data between view controllers (which was easily accomplished pre iOS 5 in multiple ways).
So to me it looks like the only advantage of using segues is that you can use storyboards and pass data between VCs.
Is that right? Or are there other advantages?
one of the down sides that can be added to Kunai Balani's answer is that it makes working with a team with version control more difficult if many people are working on the same storyboard. my svn gets really confused when 2 people make an edit on the storyboard.
if you are not working with a team then you can disregard this disadvantage
There are several advantages :
1) Communication. Storyboard (and thus use of segues) is makes it easy to understand the flow of your application. This gives other developers an ease of understanding of the structure of view controllers without looking through any code or debugging.
2) You save time by using segues. Just imagine doing push and pop everywhere all around your application. If you need to change transition (lets say modal transition animation style) for all your view-controllers you have to go and search for each and every view controller then modify it. With storyboard all of them are at one place. It's easy to modify their transition style with just modifying one attribute.
3) Ease of debugging. Lets say your application crashed during a push in navigation controllers. With story board you get the identifier for your segue which caused this. No need to follow stack trace across your UINavigation Controller.
I'm quite new in iPhone programming. I'm the only objective-c programmer of my company, and I have to create an app almost done for android but for iPhone.
I have 2 basic questions. The app has a lot of screens, a big hierarchy of views and buttons to move between the views.
Question 1: As I need a back button to go back to the previous view, is it a good idea to have like 30 or 40 view controllers and have a back button by using the UINavigationController? Or it would be better to have around 6 or 7 view controllers with many views for each view controller? [This question is made also thinking about memory management]
And Question 2: in the case that the best choice would be have 6 view controllers with many views for each view controller, how can I implement a back button as if it would be an Android app (or a UINavigationController but for UIViews)??
Thank you very much for your answers in advance, I know that memory management is a very important issue in the iPhone programming, a problem that my work-mates (android programmers) don't have, and the back button, another big problem for me depending on the way of programming the app.
Thanks a lot!!
You should have one view controller for each "screen" of content.
For the most part, the key is going to be controlling memory yourself, and ensuring that you're releasing content that doesn't need to be used at a given time. Careful maintenance of your objects should limit any memory issues you're going to have, even with numerous controllers pushing and popping from the stack.
In terms of how many controllers you should use, this is going to vary. Any screens that duplicate functions in a basic way (editing a single text field, displaying an image, etc) can usually share controllers with a little property magic worked on them before you push them.
If each of your screens is very unique, however, then having a number of view controllers won't hurt you at all.
In my iphone, in the section where I can make a call, I can view recent calls and I can also view my contacts.
I am referring to the contacts application.
I'm watching the stanford iphone vidoes, and they recommend creating a seperate NIB file for each view.
From what I understand, each nib/view will be managed by its own subclass of UIViewController.
Can someone, at a high level, describe what the contacts application might be comprised of in terms of nib's, controllers and views and how they would work together?
The contacts app is, unfortunately, a bad example. It's functionality is implemented at a lower level in the OS, as it is shared between the address book app, the phone app, and it can be implemented in your own app if you wish. Thus, the app is really just another front end for the feature.
Basically, the app is a UITableView with search that sends you to a UIView containing a UITableView and some text / image fields. Of course, there are editing and creation buttons to handle CRUD, but basically that's it. Each page would have it's own UIViewController and NIB file (assuming Apple follows their own directions, which they may not) ;)
Underneath, you have a core data store, but there's no much complexity in the data structure there, either. If you really want to analyze the database file, that's possible as well.
Hope that helps
At a high level, you have a UITabBarController that handles the tabs along the bottom and the switching of the five view controllers. Each of the view controllers, with the exception of the "Keypad" tab, uses a UITableViewController as the root controller of a UINavigationController. And it looks like, for the most part, where you are in the UINavigationController "stack" is remembered for each tab.
Each of the UITableViewControllers have a fairly simple implementation of the standard UITableViews. The implementations of UITableView are probably canonical examples of how to use UITableViews -- namely, what action to trigger depending on whether there's a disclosure button and what gets clicked.
Hope this helps!
I'm tryin to grasp the fundamentals of Cocoa (Iphone) MVC design, but it's being quite tough. I've come accross several example applications, from the web, books.. but I've found nothing related to what I'm searching, since most of the examples just present a simple app (ie, a viewcontroller with a flipside viewcontr and a bit more..). So let's see if someone is willing to help me out in pointing me to the right direction:
My goal is to build a somewhat complex app. I'd like to have the following relation of views:
Presentation view (which would have a controller loading several memory intensive vars)
Main menu view: different options that would result in entirely new complex views. In example, a Begin option to initiate whatever the app permits to do; a second option to do another complex task with different views and actions within it, an Options option to configure options; a help option, an about option, etcetera..
In a first approach I tried to embed several rounded buttons in a view under the MainWindow nib with an associated app delegate. This approach though posed the question to how I manage to switch between views/viewcontrollers. After having uncaught exceptions because I probably don't fully understand the basics, I tried to move on to more 'simple' things.
Then I came accross the Navigation and Tabbar default Cocoa controllers. I don't want a tabbar, although it could come well for other parts of this app. Then the nav controller is what I think is most suitable for this case.
Thus, am I on the right spot if I build a hierarchichal app where its root is a nav controller? I've seen I can customize the main view to display a customized table, where each cell coud act as a button to spawn its respective view+viewcontroller. From here then I can keep building the 'leaf nodes' of this hierarchy of views/viewcontrollers, right? Eventhough I don't like the animation that by default provides the nav controller, I assume I can get rid off it..
So to sum it up in an easy way: I'd like to obtain a menu like those that can usually be seen on Cocos2d apps.
It's frustrating to ask this, I know it has to be easy but I find the documentation quite a mess aswell as the examples I've seen.. GUI programming it's being a tough learning curve :/
Thank you for any answers in advance, and excuse me for this long post.
Thus, am I on the right spot if I
build a hierarchichal app where its
root is a nav controller?
Almost. A nav controller (despite being a subclass of UIViewController) does not control views but rather other view controllers. The nav controller pushes and pops the view controllers which in turn causes the controller's respective views to load and become visible.
Therefore, the "root view" is actually the view that is controlled by the view controller that is in the nav controller topViewController property.
The app delegate serves to hold the nav controller and to tell it which view controller to push on the stack first. After that, the view controllers tell the nav controller when to push and pop them.
Otherwise, you're on the right track. You should always attempt to present information on a mobile platform in an hierarchal manner starting with the most general at the top and growing more specific as you drill down.
And you shouldn't be embarrassed at finding this confusing. 90% of the introductory/tutorial info out there, including books and Apple resources, focus on the gee whiz aspects of the interface and tell you next to nothing about the actual application design or how all the parts fit together conceptually.
You right about how little information is covered about app delegates to nav controllers. I been digging and trying to get all my screens linking etc. Having alot of fun watching my apps start to look more then just some Frankenstein monster UI. ahahah
The Itunes dev videos are great for looking at push and pop stack UIviews theory. I found they moved a little fast but after watching them the hands did make more sense. I have been forcing myself to watch them all and get a really good feel for whats going on. Hopefully have a nice app working soon.
I have been struggling a little with my first real iPhone application and wanted to get some advice on how this should be structured. I am looking for some best practices in terms of creating UI components and linking them together to create the application flow (create views/controllers programmatically vs. with Interface Builder, etc...).
Overview:
I need to show a "Login" view on application start up.
--Show "Signup" view if they click the sign up button.
Once logged in... I have a TabBarController loading 4 views. These 4 views will have to load sub-views (master-detail like).
My question is:
1) What is the best way to piece this navigation structure together? Create each view as a .xib with a corresponding ViewController? How are these glued together?
2) How should I handle the Login/Sign up navigation, no TabBar should be shown on start, but will need it after authenticating the user.
Bonus Point) Are there documented best practices for this kind of stuff? I have been hacking together some workable code, but I got very lost and want to start over doing it the correct way.
I know this may be a little confusing, all and any help is much appreciated.
EDIT: For the Login view on top of the tab bar I used this, pretty simple.
LoginViewController *loginViewController = [[LoginViewController alloc] init];
[loginViewController initWithNibName:#"Login" bundle:nil];
[self.tabBarController presentModalViewController:loginViewController animated:YES];
When you create a new tab bar based application in XCode, you are pretty much already set up the way you would like - there's a main XIB that loads views for each tab from separate XIB files. You have one XIB per tab. Note that as you change types or add tabs you need to specify the proper view controller type in both the XIB with the tab bar, and in the XIB that you use to create your view!
As for the login view, a common approach is to use the tab bar as above, but in the app delegate applicationDidFinishLaunching method present a modal view controller that shows the login screen. The modal controller hides the tab bar and everything else until they are done, then it can be dismissed.
1) What is the best way to piece this navigation structure together? Create each view as a .xib with a corresponding ViewController? How are these glued together?
Use UINavigationController and push your custom views onto the navigation stack as needed. Check out the example Navigation Controller application via Xcode's New Project option to get a feel for how this works.
2) How should I handle the Login/Sign up navigation, no TabBar should be shown on start, but will need it after authenticating the user.
Set up a view for login (I would use a UITableView with one section containing two rows for username and password, but that's my own preference). Set up a second, separate view for sign-up fields (again, I would use a UITableView for this, to keep the layout clean and consistent).
Perhaps use a view animation to pop up the tab bar after successful authentication.
Bonus Point) Are there documented best practices for this kind of stuff? I have been hacking together some workable code, but I got very lost and want to start over doing it the correct way.
You'll end up rewriting your project several times — which is a good thing. Do check out Apple's sample applications (available from the iPhone ADC site) as these contain several "best practice" ways of using several of the UIKit components. As to putting together a larger application, keep your design as simple as possible and reuse as much of Apple's UI components as possible. You can always customize later.
In my opinion, only Cocoa programming examples and very simple applications are suitable for a single nib file. Otherwise you should spread your interface components across multiple nibs. This means each nib is smaller and when loaded into memory will only load those components as necessary. This will improve performance in your application and can help logically organize your program and make it easier to debug when issues arise.
In my tabbar apps I use MainWindow.xib to contain the main window and tabbar but I break up each tab into a seperate nib for the reasons above.
Apple offers the following guidelines:
When creating your nib files, try to keep the following guidelines in mind:
Design your nib files with lazy loading in mind. Plan on loading nib files that contain only those objects you need right away.
In the main nib file for a Mac OS X application, consider storing only the application menu bar and an optional application delegate object in the nib file. Avoid including any windows or user-interface elements that will not be used until after the application has launched. Instead, place those resources in separate nib files and load them as needed after launch.
Store repeated user-interface components (such as document windows) in separate nib files.
For a window or menu that is used only occasionally, store it in a separate nib file. By storing it in a separate nib file, you load the resource into memory only if it is actually used.
For more information you can visit:
http://developer.apple.com/iphone/library/documentation/Cocoa/Conceptual/LoadingResources/CocoaNibs/CocoaNibs.html#//apple_ref/doc/uid/10000051i-CH4